Many humans (and other mammals and animals) receive benefit from implantable medical devices that deliver electrical pulses to or record from desired locations within their bodies. Such medical devices may comprise, for instance, spinal cord stimulation (“SCS”) electrodes which typically comprise a small lead wire that is connected at one end to a power source and at the opposite end to a plurality of electrical contacts configured to transfer an electrical signal to the tissues that are to be stimulated. Those electrical contacts may, for instance, be situated in a paddle configured for implantation in a patient adjacent the tissue that is to be stimulated, such as along the spinal cord of a patient. SCS paddles typically have the lead wire or wires emerging from the bottom edge of the paddle, in the same plane as the body of the paddle. Also, typically there is a strain relief, molded along with the paddle, which surrounds the emerging lead or leads for approximately 5-8 mm, and beyond that the flexible leads continue onward to the power source.
SCS paddles provided with such coplanar strain relief and lead assemblies can provide certain advantages. For instance, such assembly can be advanced through an opening in the spinal canal (i.e., a laminectomy) upward or downward until the paddle and even the strain relief and a portion of the lead disappear from view. This can be useful in mapping stimulating contact positions higher or lower in the spinal canal than would be allowed by the length of the paddle alone. Moreover, molding and overall manufacturing are more easily accomplished for such configurations.
Unfortunately, however, such coplanar configurations also carry significant disadvantages. The placement of such components can be quite challenging, as the health care provider must specifically place the electrical contacts so that, when energized, they will record from or stimulate only the intended tissue, but not other tissue (stimulation of which in turn may cause perceived paresthesia, muscle contractions or even pain beyond that for which the patient originally sought treatment). In the case of traditional paddle electrode configurations, the emerging lead wire and strain relief must be bent as they emerge through an opening in bone, fascia or other tissue (for instance, laminectomy in the spine or burr hole in the skull), and to the extent that they are elastic, this introduces a bending moment, which tends to make the paddle migrate to one side or the other. Such migration will typically require surgical revision to replace the paddle in the proper position. Moreover, the techniques used to anchor such electrodes in place inside of the patient are insecure, such that the electrodes have a tendency to migrate away from the site at which they are originally implanted in the patient, at times in response to normal body movement of the patient. To the extent that it might not be anchored securely and can migrate downward, the lowermost part of a traditionally configured paddle electrode can come up and out of the spinal canal or skull, such that this part is no longer useful. Still further, during implantation, it can be quite difficult to engage a traditionally configured paddle electrode with the bony window formed by the laminectomy or burr hole, so as to mechanically lock the paddle in place within the epidural space of the spine or intracranially.
Attempts have previously been made to provide a paddle electrode in which the lead attaches to and emerges from the paddle along a face of the paddle, in turn reducing, at least to some extent, the bending moments that might be applied to the paddle from the lead. However, such prior efforts have themselves carried disadvantages, in that they prevent passage of the portion of the paddle at which the lead attaches above or below the bony window created by the laminectomy, because the nearly perpendicular emerging lead wire blocks further progress as it runs into the bony edge.
It would therefore be beneficial to provide an electrode that is more easily implanted by the health care provider in the intended position, and that is less prone to migration from the intended implantation site than previously known electrodes.